Coursework Exercises: Civil Aircraft Design (Bizjet)

Both the FPS and the SI units are worked out in the examples. Sizing calcula­tions require the generic engine data in order to obtain the factors used (see Sec­tion 10.11.3). The Bizjet drag polar is provided in Figure 9.2.

11.4.1 Takeoff

Requirements: TOFL 4,400 ft (1,341 m) to clear a 35-ft height at ISA + sea level. The maximum lift coefficient at takeoff (i. e., flaps down, to 20 deg, and no slat) is CLstall(TO) = 1.9 (obtained from testing and CFD analysis). The result is computed in Table 11.1. Using Equation 11.7a, the expression reduces to:

W/S = 4,400 x 1.9 x (T/ W)/37.5 = 222.9 x (T/ W)

Using Equation 11.7b, it becomes:

W/S = 4.173 x 1,341 x 1.9 x (T/ W) = 10,633.55 x (T/ W)

The industry must also examine other takeoff requirements (e. g., an unprepared runway) and hot and high ambient conditions.

Computing and listing in tabular form (use Figure 9.1 for the drag polar):

W/S (lb/ft2)

40

50

60

70

80

W/S (N/m2)

1,915.9

2,395.6

2,874.3

3,353.7

3,832.77

CLclimb

0.190

0.236

0.283

0.331

0.378

CD (from drag polar)

0.0240

0.0246

0.0256

0.0266

0.0282

Tsls/ W

0.340

0.310

0.286

0.272

0.265

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